全文获取类型
收费全文 | 3547篇 |
免费 | 389篇 |
国内免费 | 7篇 |
出版年
2021年 | 35篇 |
2019年 | 44篇 |
2018年 | 45篇 |
2017年 | 43篇 |
2016年 | 63篇 |
2015年 | 84篇 |
2014年 | 110篇 |
2013年 | 130篇 |
2012年 | 161篇 |
2011年 | 172篇 |
2010年 | 120篇 |
2009年 | 96篇 |
2008年 | 154篇 |
2007年 | 160篇 |
2006年 | 130篇 |
2005年 | 171篇 |
2004年 | 117篇 |
2003年 | 125篇 |
2002年 | 135篇 |
2001年 | 94篇 |
2000年 | 115篇 |
1999年 | 73篇 |
1998年 | 36篇 |
1997年 | 46篇 |
1996年 | 41篇 |
1995年 | 37篇 |
1994年 | 38篇 |
1993年 | 40篇 |
1992年 | 52篇 |
1991年 | 59篇 |
1990年 | 53篇 |
1989年 | 52篇 |
1988年 | 53篇 |
1987年 | 51篇 |
1986年 | 49篇 |
1985年 | 40篇 |
1984年 | 54篇 |
1983年 | 49篇 |
1982年 | 43篇 |
1981年 | 42篇 |
1980年 | 34篇 |
1979年 | 39篇 |
1978年 | 30篇 |
1976年 | 35篇 |
1975年 | 44篇 |
1974年 | 32篇 |
1973年 | 47篇 |
1972年 | 35篇 |
1971年 | 33篇 |
1968年 | 29篇 |
排序方式: 共有3943条查询结果,搜索用时 500 毫秒
61.
62.
63.
Analyses of plumules from seedlings of a winter wheat variety (Elgin) and a spring wheat variety (Red Bobs) indicated that SH and SS contents based on protein levels were similar in the whiter and spring wheat tissues grown at 20 C. Boll) varieties, when grown nt 3 C, contained greater concentrations of SH and SS groups, based on protein levels, than those present in the tissues grown at 20 C. The spring wheat tissues at 3 C maintained relatively constant levels of SH and SS during the growth period. Sulfhydryl (SH) and SS groups based on fresh weights were present in greater quantities in the tissues of the spring wheat grown at 20 C than in the winter wheat tissues grown at 20 C. The high SH and SS concentrations present in the warm-grown spring wheat tissues were due to a high concentration of protein extracted from that tissue. The SH and SS contents per unit fresh weight were quite similar in the cold-grown tissues of both varieties during the growth period. Both varieties at both temperatures showed a similar decrease in SH and SS contents, based on fresh weights, as maturation progressed. The spring wheats grown at 3 C and 20 C and the winter wheat grown at 3 C all showed similar characteristics and differed considerably from the winter wheat grown at 20 C. These data were positively correlated with the flowering potential of the wheat varieties. 相似文献
64.
Cathepsin C: a chloride-requiring enzyme 总被引:2,自引:0,他引:2
65.
Richard A. Ellis 《The Journal of cell biology》1965,27(3):551-563
The secretory coils of glutaraldehyde-osmium tetroxide-fixed and Epon-Araldite-embedded eccrine sweat glands from the palms of young men were studied with the electron microscope. The myoepithelial cells lie on the epithelial side of the basement membrane and abut other epithelial elements directly. The irregularly serrated base of the cell has dense thickenings along the plasma membrane which alternate with zones bearing pits; the smooth apical surface lacks dense thickenings, is studded with pits, and conjoined to secretory cells by occasional desmosomes. Masses of myofilaments, 50 A in diameter, fill most of the cell and are associated with irregular dense zones. In cross-section the arrangement of the myofilaments seems identical with that of the I band of striated muscle, and the dense zone has typical Z band structure. A few microtubules and cytoplasmic cores bearing profiles of the endoplasmic reticulum, filamentous mitochondria, and glycogen granules penetrate the fibrillar masses and run parallel to the oriented myofilaments. In the perinuclear zone, Golgi membranes, rough- and smooth-surfaced elements of the endoplasmic reticulum, mitochondria, glycogen, microtubules, lipid, pigment, and dense granules are variable components in the cytoplasm. The interrelationships of the myoepithelial cells with the secretory cells suggest that the former may act as regulators, controlling the flow of metabolites to the secretory epithelium. 相似文献
66.
67.
68.
Ann Curtis F. Millan Susan Holloway Moira Mennie Aileen Crosbie J. A. Raeburn D. J. H. Brock 《Human genetics》1989,81(2):188-190
Summary Presymptomatic testing for Huntington's disease (HD) is possible through the use of restriction fragment length polymorphisms (RFLPs) at the closely linked D4S10 locus. Recombination between the HD and D4S10 loci will occur in 4%–5% of meioses, and is a well-recognised complication of predictive testing. Recombination between RFLPs within the D4S10 locus is a rare event and can usually be ignored. We report a case where such an intra-locus recombination frustrated attempts to predict the chance of a high-risk individual inheriting the HD gene. 相似文献
69.
An additive relationship of lethality between purified protease and haemolysin of the extracellular products (ECP) of Aeromonas salmonicida was demonstrated by i.p. injection in Atlantic salmon (Salmo salar L.). The lethal toxicity of the combinations of protease and haemolysin follow a linear regression line y = -54.54x + 2400. The LD50 of protease and haemolysin when injected separately was 2400 ng/g fish and 44 ng protein/g fish, respectively. 相似文献
70.
D S Rosser M N Ashby J L Ellis P A Edwards 《The Journal of biological chemistry》1989,264(21):12653-12656
Human hepatoma HepG2 cells were used to demonstrate coordinate regulation of three enzymes of cholesterol synthesis under a variety of conditions. Addition of either delipidized serum and mevinolin or low density lipoprotein, 25-hydroxycholesterol, or mevalonic acid to HepG2 cells resulted in rapid changes both in the levels of the mRNAs and in the rates of synthesis of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) synthase, HMG-CoA reductase, and farnesyl pyrophosphate synthetase (prenyltranferase). In all cases, the changes in mRNA levels were paralleled by changes in the rates of specific protein synthesis. Pulse-chase techniques were used to determine the half-lives of all three proteins. Addition of low density lipoprotein to the media during the chase increased the rate of degradation of HMG-CoA reductase 4.6-fold but had no affect on the half-lives of HMG-CoA synthase or prenyltransferase. Therefore, we conclude that the coordinate regulation of these three enzymes under a variety of conditions occurs at the level of enzyme synthesis and not at the level of protein stability. 相似文献